Adjustable Diameter Pivot Shaft for a Hand Tool

ABSTRACT

A folding tool such as a knife has an implement such as a blade pivotally attached to the handle with a pivot shaft, allowing the implement to be rotated from a closed to an open position. The invention allows the diameter of the pivot shaft to be varied, thereby allowing the diameter of the shaft to be effectively increased in the area where the implement rotates about the shaft so that the shaft extends to and makes contact with the interior surface of the bore through the implement, without restricting the ability of the blade to freely rotate about the shaft, minimizing or eliminating any tendency of the implement to wiggle relative to the handle.

FIELD OF THE INVENTION

This invention relates to hand tools such as knives and other hand toolsthat are equipped with blades and/or other implements that are pivotallyattached to a handle, and more particularly to a method and apparatusfor adjusting the diameter of the pivot shaft that attaches the bladesand/or other implements to the handle to eliminate relative movementbetween the implement and the handle.

BACKGROUND

Folding tools such as knives have a handle with opposed halves that areheld apart to define a blade-receiving space. A blade is pivotallyattached to the handle with a pivot shaft or axle that has its oppositeends secured to the opposite handle halves, and which extends through abore in the blade. The pivot shaft defines a strong and secureconnection between the blade and the handle about which the blade may bepivoted between a closed position in which the blade is stowed safely inthe handle, and an open position in which the blade extends away fromthe handle for normal use.

Although there are many different kinds of structures used for pivotshafts used to attach knife blades to knife handles, an inherent problemwith pivoting knives (and other folding tools) is that there is almostalways a certain amount of play between the blade and the handle. Thus,in order to enable the blade to pivot freely about the pivot shaft,there must be some tolerance between the outer diameter of the pivotshaft and the inner diameter of the bore in the blade through which theshaft extends. In high quality knives the amount of clearance betweenthe blade bore and the shaft can be minimized, but there still must beenough tolerance to allow the blade to be pivoted relatively easily.This necessary tolerance results in rotational movement of the blade,which is perceived as wobble between the blade and the handle: thisphenomena is often colloquially referred to as “tip wobble.”

Tip wobble is undesirable because it necessarily reduces the strength ofthe blade/handle connection. In extreme cases, tip wobble can result inan unsafe tool—this is sometimes a concern with lower quality foldingknives. But tip wobble is often present even in the most highlyengineered and expensive folding knives and can be both a bother and astructural limitation.

There are several common techniques utilized to eliminate, or at leastminimize the amount of tip wobble. The most common approach is simply toreduce the tolerance between the blade bore and the pivot shaft—thecloser the tolerance between the pivot shaft and the bore, the lesserthe tip is able to wobble. The trade off with this approach is of coursethat a certain amount of spacing between the blade and the shaft isnecessary to allow the blade to pivot freely. With automatic orsemi-automatic style knives, an easily pivoting blade is a necessity. Assuch, this approach has its limitations. Another approach is to add alow-friction bushing around the pivot shaft so that the shaft—boretolerance may be minimized. As with the other techniques just described,this is an effective way to help minimize tip wobble, but it does noteliminate wobble. Moreover, the bushings tend to wear and degrade overtime and as they do so, tip wobble tends to increase.

Another solution relies upon a blade-locking mechanism to minimizerelative movement between the blade and handle Some locking mechanismsutilize a 3 point-of-contact lock that forces out the play in the pivotbore. While this technique does help minimize blade movement, not allknife designs can incorporate these kinds of locking mechanisms. Othercommon locking mechanisms do not alleviate tip wobble.

There is an ongoing need therefore for manufacturing techniques andmethods that reduce tip wobble in folding tools such as knives.

The present invention relates to an apparatus and method forestablishing a strong, secure interconnection between a folding toolimplement and the handle of the folding tool, and which minimizes oreliminates tip wobble while insuring that the implement may be easilypivoted between the open and closed positions. The invention allows thediameter of the pivot shaft to be varied, thereby allowing the diameterof the shaft to be effectively increased so that the shaft extends toand makes contact with the interior surface of the bore through theblade, without restricting the ability of the blade to freely rotateabout the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and its numerous objects andadvantages will be apparent by reference to the following detaileddescription of the invention when taken in conjunction with thefollowing drawings.

FIG. 1 is a side elevation view of a folding knife of the type thatincorporates the adjustable diameter pivot shaft according to thepresent invention, illustrating the blade of the knife in an openposition.

FIG. 2 is a side elevation view of the folding knife shown in FIG. 1with a portion of the near-side handle removed to expose the near-sideliner and other internal structures of the knife.

FIG. 3 is a cross sectional view taken along the line 3-3 of FIG. 1.

FIG. 4 is a cross sectional view taken along the line 4-4 of FIG. 3,showing only that portion of the knife and its structures around theblade/handle interconnection.

FIG. 5 is a perspective exploded view of the knife shown in FIG. 1.

FIG. 6 is a perspective exploded view of the adjustable diameter pivotshaft according to the present invention.

FIG. 7 is a perspective partial cross sectional view of a portion of theknife shown in FIG. 1 where the blade interconnects with the handle, andwith the blade shown in the open position.

FIG. 8 is a cross sectional view similar to the view of FIG. 3,illustrating an alternative embodiment of the adjustable diameter pivotshaft.

FIG. 9 is a cross sectional view similar to the views of FIGS. 3 and 8,illustrating another alternative embodiment of an adjustable diameterpivot shaft.

FIG. 10 is a perspective exploded view of the embodiment of theadjustable diameter pivot shaft shown in FIG. 9.

FIG. 11 is a cross sectional view of the embodiment of the adjustablediameter pivot shaft shown in FIG. 8, illustrating an alternativemechanism for adjusting the diameter of the pivot shaft.

FIG. 12 is a cross sectional view of the embodiment of FIG. 11illustrating a resilient ring that functions to maintain the position ofthe internal threaded screw.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first illustrated embodiment of a folding knife 10 incorporating anadjustable diameter pivot shaft according to the present invention isillustrated in FIGS. 1 through 7. A first illustrated alternativeembodiment of the folding knife that includes an adjustable diameterpivot shaft according to the present invention is illustrated in FIG. 8.It will be appreciated that the present invention is described herein asit is used in a folding knife, but that the invention is equallyapplicable to other kinds of folding tools that have implements otherthan the knife blades described herein. Thus, the principals of theinvention and the structures that enable the invention may be used inmany kinds of folding tools other than knives. Description of theinvention as it is used with a knife should thus be considered a way ofenabling the invention for those of skill in the art, but not as alimitation to the scope of the invention as defined in the claims.

Folding knife 10 includes an elongate handle 12, and a blade 14 that ispivotally attached to the handle at one of its ends—referred to hereinas the “forward” end 16 of the handle. Other relative directional termscorrespond to this convention: the “rear” or butt end 18 of the handleis opposite the forward end; the “upper” part 20 of the blade is thedull, non-working portion and the “lower” part 22 of the blade is thesharpened, working portion; “inner” or “inward” refers to the structuralcenter of the knife 10, and so on. FIGS. 1 and 2 show the knife 10 withthe blade 14 in the open position. An X-Y-Z axis grid is shown inFIG. 1. The X-Y plane is defined as the plane parallel to the planedefined by the handle 12 and blade 14—the blade travels in the X-Y planeas it is rotated between the closed and open positions. The Z plane isthe plane transverse to the X-Y—as detailed below, the blade pivot shaftextends longitudinally in the Z-plane.

With reference now to FIG. 5, the various components of knife 10 will bedescribed. Handle 12 of knife 10 comprises several components, includinga pair of oppositely located handle halves, generally indicated at 24,26, that are parallel with each other and held spaced apart from oneanother by a spacer 28 that is attached between the handle halves alongan upper edge thereof. Each of the handle halves 24 and 26 comprise aninner liner and an outer plate that are held parallel to one another.Specifically, handle half 24 is defined by liner 30 and an outer plate32. Likewise, handle half 26 is defined by liner 34 and outer plate 36.It will be noted that each of the outer plates 32 and 36 includes adecorative center section (32 a and 36 a, respectively) that isseparately attached to the outer plate. It will be understood that thedecorative sections 32 a and 36 a could be replaced by making the outerplates solid without the separable decorative sections. Moreover, itwill be understood that the handle halves 24 and 26 may be unitary inconstruction—that is, there is no reason that the handle halves includea liner and an outer plate.

The handle 12 is assembled with blade 14 with various screws and spacersas best shown in FIG. 5. Thus, blade 14 is pivotally connected to handle12 with a pivot shaft assembly 100, which is described in much greaterdetail below, and which extends through aligned bores 38 in outer plate32 and 40 in liner 30, bore 102 in blade 14, and bores 42 in liner 34and bore 44 in outer plate 36. As detailed below, the interior diameterof bore 44 is formed in a series of planar faces. A screw 46 extendsthrough aligned bores in the rearward portion of the handle halves andthe spacer and is threaded into a nut/spacer 48, and a similar screw 50and nut/spacer 52 are located midway along the length of handle 12 alongthe upper margin such that the screw spacer 42 extends through thehandle halves and the spacer 28. Additional screws may be used in aconventional manner to secure the handle components together and so thata blade-receiving groove 54 (see e.g., FIG. 3) is defined between thehandle halves 24 and 26. The blade receiving groove 54 defines a slotinto which the blade 14 is received when it is moved to its closedposition. When the blade is in the closed position, the sharp edge 22 ofthe blade is held safely within the confines of the handle. Spacers 48and 52 are preferably cylindrical sleeves that have a threaded internalbore into which screws 46 and 50 are threaded. The screws thus securethe spacers between the handle halves 24 and 26 to maintain the handle12 in a secure relationship with handle halves 24 and 26, which are heldin a spaced apart relationship. The handle halves 24 and 26 may befabricated from any suitable material such as metal, a reinforcedsynthetic plastic; other suitable materials include metal, otherplastics, wood, etc. The handle halves sections may be fabricated insingled or multiple pieces, as shown in FIG. 5. Decorative sections 32 aand 36a may be any kind of material such as fine wood. As shown in FIG.5, a loop 54 may be added to the rearward end of spacer 28 to define alocation to attach a lanyard (not shown) to the knife 10.

Continuing with FIG. 5, knife 10 is shown as including an optional bladelocking mechanism 56, which is formed as part of liner 34. Lockingmechanism 56 does not form a part of the present invention and istherefore not described in great detail. Nonetheless, the lockingmechanism 56 is defined by a spring arm 58 formed in liner 34 that has atooth 60 formed on the forward end 62 of the spring arm. Spring arm 58is normally biased under spring force inwardly, toward blade 14 in theassembled knife so that when the blade is in the open position the tooth60 cooperates with a notch 64 in the tang portion 66 of blade 14 to lockthe blade in the open position. A stop pin 68 is secured between liners30 and 34 and stops rotation of blade 14 in the open position byabutting a cooperatively formed notch 70 in the tang 66 of blade 14.Thus, when the blade 14 is in the fully open position of FIG. 1, stoppin 68 is in an abutting relationship with notch 70 and lockingmechanism 56 is locked such that tooth 60 is engaging notch 64.

As noted, the blade 14 is pivotally attached to the handle 12 near theforward end of the handle with a pivot shaft assembly 100. Blade 14 isattached to handle 12 such that the blade's working portion 22 extendsaway from the handle 12 when the blade 14 is in its open position (FIG.1), and tang portion 66 is located within the blade receiving groove 54between the paired handle halves when the blade is in either the open orthe closed position. That is, the tang portion 66 is always locatedbetween the handle halves 24 and 26 of handle 12. The blade is pivotallyattached to the handle with pivot shaft assembly 100, which extends inthe Z direction, transverse to the plane of the blade.

The pivot shaft assembly defines a blade pivot axis—the axis is thecenterline through the pivot shaft that extends in the Z direction,transverse to the X-Y plane. Pivot shaft assembly 100 is shown inisolation in FIG. 6 and includes a cylindrical sleeve or shaft 104, ascrew 106 that threads into first end 105 of the hollow, threadedinterior 108 of shaft 104, and a set screw 110 that threads into secondend 107 of the threaded interior 108 of shaft 104. As noted, shaft 104has a hollow, threaded interior 108 so that the shaft defines a hollowcylinder. Second end 107 of shaft 104 has an oversized lip 112 and aseries of planar faces 114 on the inner-facing side of the lip. Theshaft has three bores formed approximately midway along its length, twoof which are shown in FIG. 6 and which are identified with referencenumbers 120 and 122. The third bore is identified with reference number124. The three bores 120, 122 and 124 are axially arranged and evenlyspaced around the shaft. Three ball bearings, labeled with referencenumbers 126, 128 and 130 are received into the bores 120, 122 and 124,respectively. A fourth ball bearing 132 is received into the interior ofshaft 104 and as detailed below, and is located between the interior end134 of screw 106 and bearings 126, 128 and 130 in the assembled knife10.

The pivot shaft assembly is assembled with knife 10 by inserting theshaft 104 through bore 44 in outer plate 36 until the series of planarfaces 114 rest in the cooperatively formed bore 44. This cooperativegeometric relationship between the planar faces 114 of shaft 104 and theplanar faces of bore 44 prevents the shaft 104 from rotating relative tothe outer plate 36. The shaft 104 is inserted through bore 42 in liner34, bore 102 in tang portion 66 of blade 14, bore 40 of liner 30 andbore 38 of outer handle 32. The outer diameter of shaft 104 is slightlysmaller than the diameter of bore 102. Stated another way, there is someclearance between the outside of the shaft and the inner surface 103 ofthe bore 102.

A first washer 136 is placed around shaft 104 between the inner-facingside of liner 34 and blade 14, and a second washer 138 is similarlyplaced between the inner-facing side of liner 30 and blade 14. With theshaft positioned with the handle components as just described, screw 106is threaded into first end 105 of shaft 104 and is tightened. Again,shaft 104 is prevented from rotating as screw 106 is tightened becausethe series of planar faces 114 and the cooperative planar faces in bore44. As seen in FIG. 3, when screw 106 is tightened in place, bores 120,122 and 124 are aligned in handle 12 with the centerline of blade 14. Atthis point, ball bearing 132 is inserted into second end 107 of shaft104. Ball bearing 132 rests on the interior end 134 of screw 106. Next,bearings 126, 128 and 130 are inserted into second end 107 of shaft 104.Each of these bearings is received into the respective bores 120, 122and 124 in shaft 104.

Set screw 110 is next threaded into shaft 104. The inner tip 140 of setscrew 110 is smoothly tapered. As such, when the set screw is threadedinto the interior of shaft 104, the tapered tip 140 bears against thethree bearings 126, 128 and 130 and these three bearings also bearagainst bearing 132, which naturally assumes its position the center ofthe three bearings 126, 128 and 130 as pressure is applied to thebearings with set screw 110. Optionally, a circularly concave divot 142(see FIG. 5) may be formed in the axial center of the interior end 134of screw 106 to located and position bearing 132, although as noted thebearing 132 will normally assume this position as set screw 110 istightened.

It will be appreciated that as set screw 110 is threaded more tightlyinto shaft 104 and bears against the bearings, the three bearings 126,128 and 130 are forced outwardly from the axial centerline through theshaft, through the bores 120, 122 and 124, as illustrated with arrows Ain FIGS. 3 and 4. This force is directed in the X-Y plane as set screw110 is threaded inwardly in the Z direction. As set screw 110 is screwedmore tightly against the bearings, the bearings are forced with greaterpressure against the interior surface 103 of bore 102 through blade 14,effectively increasing the diameter of the pivot shaft and similarlyeffectively decreasing to zero the clearance between the pivot shaft andthe blade. And although the diameter of the pivot shaft 104 has in thismanner been increased so that the tolerance between the blade and theshaft is zero, the blade is easily rotated about the shaft between theopen and closed positions by virtue of the bearings, which rotaterelatively freely as the blade is rotated between the open and closedpositions—the inner surface 103 of the bore 102 through blade 14 rotatesover the bearings as the blade is moved from open to closed, and fromclosed to open.

Optionally, the set screw 110 described above with the tapered end couldbe replaced with a set screw having a planar inner surface and using afifth ball bearing between the planar end of the set screw and theaxially arranged bearings.

The amount of pressure applied by the bearings against the blade may beadjusted by varying the position of set screw 110. Because the bearings126, 128 and 130 are bounded by the bores in which the bearingsreside—that is, bores 120, 122 and 124, the bearings are urged only inthe direction of arrows A, in the X-Y plane. In other words, anytendency of the bearings to be driven in any direction other than in theX-Y plane when set screw 110 is tightened is eliminated because thebores define the only route that the bearings are able to move. Setscrew 110 may optionally include means for fixing the position of thescrew to prevent loosening, such as nylon locking materials or otherconventional screw locking mechanisms. Moreover, the set screw shown inthe drawings utilizes a hex-type head, but any kind of set screwadjustment head may be used. Furthermore, bearing 132 may be eliminatedby fabricating the inner end of screw 106 so that it replicates theshape of bearing 132.

Pivot shaft assembly 100 thus allows the effective diameter of the pivotshaft to be varied, and in the assembled knife 10 the diameter of theshaft is increased by screwing set screw 110 into shaft 104. This forcesbearings 120, 122 and 124 outwardly so that they bear against theinterior surface 103 of the bore 102 through blade 14. Because thebearings put pressure on the blade, tip wobble is eliminated. All of thebearings are preferably metallic or ceramic so that the blade 14 pivotssmoothly and easily between the closed and open positions.

A first alternative embodiment of an adjustable diameter pivot shaftaccording to the present invention is shown in FIG. 8. There, pivotshaft assembly 200 includes a cylindrical sleeve or shaft 204, a screw206 that threads into first end 205 of the hollow, threaded interior 208of shaft 204, and a set screw 210 that threads into second end 207 ofthe threaded interior 208 of the shaft. Second end 207 of shaft 204 hasan oversized lip 212 and is seated in outer plate 36 to prevent relativerotation between the shaft and the plate in the same manner describedabove with assembly 100. The shaft 204 has three bores formedapproximately midway along its length, two of which are shown in FIG. 8and which are identified with reference numbers 220 and 222. Three ballbearings, two of which are shown in FIG. 8 and labeled with referencenumbers 226 and 228 are received into the bores 220 and 222,respectively (and the third bearing, which is not visible, is receivedinto the third bore in the manner described above—although the thirdbore is not visible in FIG. 8). A first elastomeric pad 230 is locatedadjacent the interior end of screw 206 and a second elastomeric pad 232is located adjacent the interior end of set screw 210, the interior endof which is flat, unlike the interior end of set screw 110 which issmoothly tapered. Fourth ball bearing 234 is positioned between firstelastomeric pad 230 and bearings 226, 228 and the third bearing, andfifth ball bearing 236 is positioned on the other side of the threecentral bearings (226, 228, and the third bearing which is not visiblein FIG. 8), between the central bearings and the second elastomeric pad232.

The pivot shaft assembly 200 is assembled with knife 10 similarly to theprocess described above. Thus, shaft 204 is inserted through the boresin outer plate and inner plate, the blade, and the inner and outer plateon the opposite side of the blade. Washers 136 and 138 are placed aroundshaft 204 on opposite sides of the blade between the inner-facing sideof the liners and the blade. With the shaft positioned with the handlecomponents, screw 206 is threaded into first end 205 of shaft 204 and istightened, thereby aligning bores 220 and 222 with the center of blade14. At this point, ball bearing 234 is inserted into second end 207 ofshaft 204. Ball bearing 234 rests on the first elastomeric pad 230 onthe interior end of screw 206. Next, bearings 226, 228 and the thirdbearing are inserted into second end 207 of shaft 204. Each of thesebearings is received into the respective bores in shaft 204. Fifthbearing 236 is then inserted into the shaft. At this point the threecentral bearings are each received into the respective bores in theshaft and the fourth and fifth bearings 230 and 232 are located in thecenter of the axially arranged three central bearings, 226, 228 and thethird bearing, occluded in the view of FIG. 8.

Second elastomeric pad 232 is then inserted into second end 207 of theshaft, and set screw 210 is threaded into the shaft. When the set screwis threaded into the interior flat face of the screw bears against thesecond elastomeric pad 232, putting pressure on bearing 236, which asnoted is positioned in the center of the three central bearings as shownin FIG. 8. This compresses all of the bearings inwardly, causingbearings 226, 228 (and the third bearing, not visible) to be forcedoutwardly from the axial centerline through shaft 204 in the directionof arrows A, so that the bearings apply pressure against the innersurface 203 of the bore through the blade. As set screw 210 is threadedmore tightly into shaft 204 and compresses the bearings, the threecentral bearings 222, 228 are forced in the X-Y plane, effectivelyincreasing the diameter of the pivot shaft and similarly effectivelydecreasing to zero the clearance between the pivot shaft and the blade.

A second alternative embodiment of an adjustable diameter pivot shaftaccording to the present invention is shown in FIGS. 9 through 12.There, pivot shaft assembly 300 includes an outer sleeve 302 that hasplural slots 304 formed therein in the manner of kerf cuts forming acollet. The sleeve is manufactured from a resilient material such asspring steel and the slots allow the sleeve to either expand (and thusincrease the outer diameter of the sleeve) or contract (and thusdecrease the outer diameter of the sleeve). The outer sleeve 302 has atapered internal 306 surface that is received on a shaft 308 that has anoppositely tapered outer surface 310. As detailed below, when the shaft308 is moved axially relative to the sleeve 302, the outer surface 310pushed against the internal surface 306, which causes the sleeve 302 toexpand so that the diameter of the sleeve and thus the diameter of thepivot shaft is increased. It is preferable that the outer sleeve 302cannot rotate around the shaft 308, for instance when the blade is movedbetween the open and closed positions. Means are thus provided toprevent the sleeve from rotating on the shaft. While there are numerousstructures that may be used to prevent rotation of the sleeve on theshaft, as one example in FIG. 10, a tab 305 on the tapered outer surface310 of shaft 308 aligns in one of the slots 304 of sleeve 302 to preventthe sleeve from rotating on the shaft when assembled together.

The shaft 308 has threaded opposite ends, labeled 312 and 314 in FIG.10, a tapered center section that defines tapered surface 310, andflattened portion 316 on both sides of the center section. In theassembled knife, the threaded end 312 is threaded into a first set screw318 and the opposite threaded end 314 is threaded into a second setscrew 320. A washer is positioned on both sides of the blade 14, betweenthe blade and the liners 32 and 34. Specifically, a washer 322 has aD-shaped central opening with a flattened portion 326 that mates withflattened portion 316 on shaft 308. A tab 328 on an outer peripheraledge of the washer is received into a slot 330 in liner 34. Thecombination of the tab 328 received in the slot 330, and the flattenedportion 316 on shaft 308 mating with the cooperative flattened portion326 on the washer, define an anti-rotation mechanisms that preventsshaft 308 from rotating in the assembled knife. Another manner ofbuilding in the anti-rotation feature is to form a D-shaped opening inthe liners 32 and 34, thus eliminating the need for the D-shaped openingin the washers, and the tabs 328.

The pivot shaft assembly 300 is assembled with knife 10 as shown in FIG.10 by sliding sleeve 302 over the central, tapered portion of the shaft308 such that the tapered interior surface 306 of sleeve 302 nestsagainst the oppositely tapered outer surface 310 of shaft 308. The shaftis then inserted through the pivot bore in blade 14 and the washers 322and 324 are slid over the opposite ends of the shaft with the flattenedportions aligned. The blade and pivot shaft assembly is then assembledwith the handle halves, and the set screws 318 and 320 are insertedthrough the bores in the handle and threaded onto the ends of the shaft308. It will be appreciated that the outer surface of the sleeve 302defines the surface on which blade 14 rotates and, as best seen in FIG.9. As such, the outer surface of the sleeve 302 is preferably polishedsmoothly and/or coated with compounds tending to smooth the surface. Asalso seen in FIG. 9, one end of the sleeve 302 abuts washer 324, in FIG.9 the end of the sleeve on the left side of the drawing, preventing thesleeve from moving toward the left.

With the knife 10 assembled, the diameter of the pivot shaft is adjustedto provide the desired tolerance between the sleeve 302 and the bore inthe blade. This is done, for example with reference to the embodiment ofFIG. 9, by loosening screw 318 slightly and then either tightening orloosening screw 320. As screw 320 is adjusted, shaft 308 is pulled orpushed axially in the direction transverse to the major plane of blade14—that is, in the direction of arrow B in FIG. 9. As the shaft moves inthis direction, the tapered outer surface of the central portion ofshaft 108 moves relative to the oppositely tapered inner surface 306 ofsleeve 302, which as noted previously abuts washer 324 and is unable tomoving in the direction toward that washer. As the shaft thus movesrelative to the sleeve the diameter of the sleeve increases or decreases(depending upon which direction the shaft is being moved), as shown witharrow A (illustrating an increase in the diameter of the sleeve). Asdescribed previously, sleeve 302 includes plural slots 304 that allowthe sleeve to expand or contact in the manner of a collet. It will beapparent that as the tapered surfaces 306 and 310 move relative to andagainst one another, the outer diameter of the sleeve gets larger orsmaller depending on the direction that the shaft is moved relative tothe sleeve. More specifically, with continuing reference to FIG. 9, withscrew 318 slightly loose, as screw 320 is tightened (i.e., rotatedclockwise), shaft 308 is pulled into screw 320 (to the left in the viewof FIG. 9). As the shaft moves and tapered outer surface 310 movesrelative to tapered inner surface 306, the diameter of sleeve 302increases. It will thus be appreciated that the diameter of sleeve 302is decreased by loosening screw 320.

With the diameter of the pivot shaft set to the desired position, screw318 is tightened to complete the assembly process. It will beappreciated that by varying the tolerance between the sleeve 302 and theblade 14, the amount of force required to rotate the blade about thepivot shaft from closed to open, and vice versa, may be varied.

FIG. 11 illustrates a pivot shaft assembly 300 that is substantially thesame as the pivot shaft described above and shown in FIGS. 9 and 10,insofar as it includes an expandable sleeve 302, but shows analternative mechanism for adjusting the position of shaft 308 in thehandle and thus the diameter of the pivot shaft. In FIG. 11, screw 318has a hex wrench opening 350 which is a through opening that opens tothe interior of the screw. The outer end of shaft 308 includes a hexopening 352 that is smaller in size than opening 350. To adjust thediameter of the pivot shaft, a hex wrench that fits hex opening 352 isinserted through opening 350 to engage hex opening 352 and to rotate theshaft 308, and thereby move the shaft in the left or right direction inFIG. 11 (i.e., arrow B). As described above, this enlarges or decreasesthe diameter of sleeve 302. With the mechanism shown in FIGS. 11 and 12it is necessary to rotate the shaft 308 to move the shaft axially; assuch, the washers 322 and 324 do not include the anti-rotationstructures described above with reference to FIG. 9.

The pivot shaft assembly shown in FIG. 12 is identical to that shown inFIG. 11, but further includes a resilient ring 340 surrounding the pivotshaft 308 between washer 324 and a seat 342 formed in screw 320 forretaining the resilient ring. When the knife 10 is assembled, theresilient ring is compressed and this causes pressure to be exertedagainst washer 324 and thus on sleeve 302, which is abutting the washer.The pressure applied to sleeve 302 maintains the sleeve in the desiredposition and thus maintains the desired diameter of the pivot shaft.

Returning to FIG. 10, it will be recognized that there are numerousmanners in which slots 304 may be formed in the sleeve 302 in order toallow the sleeve to be enlarged. The slots 304 shown in the figureextend roughly parallel to the axis through the sleeve. However, theslots could be oriented at angles relative to the axis, or radially orin other geometric configurations. Unlike the embodiments illustrated inFIGS. 1 through 8 and described above, in which the ball bearings makepoint contact with the tang of the blade, with the embodiment shown inFIGS. 9 through 12 there is contact between the outer surface of outersleeve 302 and the bore through the tang of the blade over the entiresurface of the sleeve. This results in a relatively strongerconfiguration and contributes to minimization of relative movementbetween the blade and the handle when the blade is in the open position.

Those of skill in the art will readily appreciate that from a functionalpoint of view, the pivot shaft assemblies 100, 200 and 300 describedabove and shown in the drawings serve to vary the diameter of the pivotshaft, and as noted, in doing so as the diameter of the pivot shaftincreased, decrease the clearance between the pivot shaft and the blade(or other implement) to zero. There are many equivalent structures tothose described herein that may be employed to accomplish thesefunctional objectives. For example, a cassette of needle bearings may beused with the pivot shaft, fitted with mechanisms to urge the needlebearings outwardly from the shaft. Roller bearings likewise may beutilized. These modifications illustrate that the number of bearings isnot fixed at three, but can be as few as two bearings and include morethan three. Thus, for example, the sleeve 104 could include more thanthree bearings if desired.

While the present invention has been described in terms of a preferredembodiment, it will be appreciated by one of ordinary skill that thespirit and scope of the invention is not limited to those embodiments,but extend to the various modifications and equivalents as defined inthe appended claims.

1. A hand tool having an adjustable diameter pivot shaft, comprising: ahandle having first and second handle halves held in a spaced apartrelationship to define an implement groove between the handle halves; animplement pivotally connected between the handle halves with a pivotshaft extending through a bore in a tang portion of the implement, thepivot shaft attached to the handle halves so that the implement ismovable between an open position and closed position about said pivotshaft; wherein said pivot shaft is defined by an outer sleeve thatextends through the bore in the implement and an inner shaft extendingthrough the interior of the outer sleeve, said inner shaft being axiallymovable relative to the outer sleeve, and wherein movement of the innershaft causes the diameter of the outer sleeve to change.
 2. The handtool according to claim 1 wherein the outer sleeve has a tapered innersurface that contacts an oppositely tapered surface on the pivot shaft.3. The hand tool according to claim 2 wherein movement of the innershaft in a first direction relative to the outer sleeve causes thediameter of the outer sleeve to increase.
 4. The hand tool according toclaim 1 wherein the outer sleeve has a plurality of slots formedtherein.
 5. The hand tool according to claim 1 including means toprevent said outer sleeve from rotating around said inner shaft.
 6. Thehand tool according to claim 5 wherein the means to prevent said outersleeve from rotating around said inner shaft includes a tab formed on asurface of the inner shaft that is received in a cooperative slot in theouter sleeve.
 7. The hand tool according to claim 1 including means toprevent rotation of the inner shaft.
 8. In a hand tool having a handlehaving first and second handle halves held in a spaced apartrelationship to define an implement groove between the handle halves, animplement pivotally connected between the handle halves with a pivotshaft extending through a bore in a tang portion of the implement, thepivot shaft having a pivot shaft axis and attached to the handle halvesso that the implement is movable between open position and closedpositions about said pivot shaft, the improvement comprising: anexpandable sleeve around said pivot shaft, said expandable sleeveextending through the bore in the tang portion of the implement andwherein movement of said pivot shaft along the axis thereof causes theexpandable sleeve to expand.
 9. The hand tool according to claim 8wherein the diameter of the pivot shaft may be increased so that theentire outer surface of the expandable sleeve is in contact with aninterior surface of the bore in the tang portion of the implement. 10.The hand tool according to claim 8 wherein the expandable sleeve has atapered inner surface that makes contact with an oppositely taperedouter surface of said pivot shaft.
 11. The hand tool according to claim10 wherein movement of the pivot shaft in a first direction relative tothe expandable sleeve causes the tapered inner surface of the expandablesleeve to move on the oppositely tapered outer surface of the pivotshaft to increase the diameter of the expandable sleeve.
 12. The handtool according to claim 10 wherein the expandable sleeve has a pluralityof slots formed therein.
 13. The hand tool according to claim 8 whereinthe expandable sleeve cannot rotate relative to the pivot shaft.
 14. Ina hand tool having a handle and an implement pivotally attached to thehandle, a method of reducing relative movement between the handle andthe implement when the implement is in an open position, the methodcomprising the steps of: a) rotatably attaching the implement to thehandle by passing a pivot shaft through a pivot shaft bore in theimplement, the inner diameter of the pivot shaft bore being greater thanthe outer diameter of the pivot shaft, and attaching the opposite endsof the pivot shaft to opposed handle halves; and b) increasing thediameter of the pivot shaft until the pivot shaft contacts the innerdiameter of the pivot shaft bore.
 15. The method according to claim 14including the steps of providing the pivot shaft having a centrallongitudinal axis with plural bores extending through an outer surfaceof the shaft into a hollow core of the shaft, and inserting ballbearings into each of said bores.
 16. The method according to claim 14including the steps of providing the pivot shaft with an expandablesleeve having an outer diameter, and causing the outer diameter of theexpandable sleeve to increase.
 17. The method according to claim 16wherein the pivot shaft has an axis and step b) includes the step ofmoving the pivot shaft axially relative to the expandable sleeve
 18. Themethod according to claim 17 wherein moving the pivot shaft axiallycauses pressure to be exerted against the expandable sleeve and causesthe outer diameter of the expandable sleeve to increase.
 19. The methodaccording to claim including the step of preventing the expandablesleeve from rotating around the pivot shaft as the as the implement isrotated.
 20. The method according to claim 19 including the step ofpreventing rotation of the pivot shaft relative to the handle.